Valder Steffen

Valder Steffen Jr obtained his Mechanical Engineering degree in 1976
from Campinas State University (UNICAMP), in Brazil. He received his Doctorate
in Mechanical Engineering in 1979 from the University of Franche-Comté, Besançon,
France. He also had his Habilitation to
direct research (H.D.R) in 1991 from the University of Franche-Comté. Prof. Steffen
has co-organized a textbook, authored and co-authored more than two hundred
scientific publications in international journals, conference proceedings, and
book chapters, on the subject of dynamics of mechanical systems.

He is an associate editor of the Journal of Vibration and Control, the
Shock and Vibration Journal, the Latin American Journal of Solids and
Structures. He is a member of the Society for Experimental Mechanics (SEM), and
a member of the Brazilian Society of Mechanical Sciences and Engineering
(ABCM).

He has coordinated and participated of various national and
international research projects in the area of dynamics of mechanical systems
and has been responsible for the organization of various national and
international conferences promoted by ABCM (at the moment he is one of the
Chairmen of the International Symposium on Dynamic Problems of Mechanics –
DINAME 2015).

His current research interests are rotor dynamics, direct and inverse
problems in engineering, smart structures, and structural health monitoring.

SMART ROTORS DESIGN

Valder Steffen Jr

Federal University of
Uberlândia

School of Mechanical
Engineering

Uberlândia – MG –
Brazil

vsteffen@mecanica.ufu.br

Abstract

An important trend in rotor dynamics design is to obtain smart rotors.
Smart rotors in this context represent machines that are able to adapt to
various working conditions by incorporating smart technology. In the case of
flexible rotors, control techniques are mandatory. The control approaches for
rotating machines are clustered into three main categories, namely passive,
active, and semi-active techniques. Passive techniques are normally performed
by devices known as absorbers or isolators. These techniques are effective over
a limited frequency bandwidth and, consequently, are unable to adapt their characteristics
to changes in the system. Differently, active approaches promise vibration suppression
over a broadband of frequencies in which the suppression is performed by incorporating
active actuators, such as PZT stacks, magnetic bearings, and electromagnetic actuators
to the machine to act directly against the vibratory loads. In semi-active
approaches, the vibration is attenuated through an indirect manner by changing
the structural parameters of the machine, such as damping and/or stiffness. Another
important issue in rotor dynamics is the so-called structural health monitoring
techniques (SHM)for crack detection in rotating machines. In general,
vibration based approaches are not able to detect incipient cracks. For this
reason, using smart material technology, incipient faults in rotating shafts can
be detected by using the electromechanical impedance method. This technique
measures the electromechanical impedance of the structure by using patches of
piezoelectric material (PZT patches) bonded on the surface of the structure (or
embedded into it). Through the PZT sensor-actuators, the electromechanical
impedance, which is directly related to the mechanical impedance of the
structure, is obtained. Based on changes of the impedance signals (e.g., due to
the growing crack), the damage can be detected. Consequently, the present
contribution is dedicated to the presentation of various smart technologies
applied to rotor dynamics design thus giving an overview of several available
methods to monitor and evaluate the dynamic behavior of rotating machines, so
that control techniques can be successfully applied.